Automatic telephone system



Oct. 13,1925. 1.556.151

w. A. BENSON I AUTOILTIC TELEPHUNE S'YSTEK .Filed June 15-, 1921 v V I17.11am fi-Bansmn v I 'Z-W Patented 0a. 13, 1925.

UNITED STATES PATENT orrlcs.

WILLIAM A. BENSON, OI CHICAGO, ILLINOIS, ASSIGNOB TO AUTOMATIC ELECTRICCOMPANY, 01 CHICAGO, ILLINOIS, A CORPORATION 01' ILLINOIS.

AUTOMATIC I TELEPHONE SYSTEE.

Application fled June 13, 1881. Serial. No. 477,188.

To all whom it may cone-em;-

Be it known that I, WILLIAM A. BENSON, a citizen of the United States ofAmerica, and a resident of Chicago, Cook County, and State of Illinois,have invented certain new and useful Improvements in Automatic TelephoneSystems, of which the following is a specification.

The present invention relates in general to automatic telephone systems;and the particular object of the invention is to pro vide means, when abusy line is called, for notifying the subscriber on the called busyline that a connection is desired with his line.

' The above and other objects of the invention' will be described fullyhereinafter with reference to the accompanying drawlieferring now to thedrawin at A is shown a subscribers substation o the usual automatictype. The line conductors extending to the substation terminate at theexchange in an individual trunk selecting or line switch 0. This lineswitch is of the well known rotary type whose wipers have no normalposition, always remaining, when which have been modified in accordancewith the features of my invention. The connector H has access to calledlines such as the one shown associated with the substation A. At theexchange the line of the substation A terminates in the individual lineswitch C. 7

At I is shown a constantly operating interrupter the function of whichwill be explained hereinafter.

While in the drawin the line switch C is shown having access irectly toconnector switches, it will be readily apparent that as many selectorsas are necessary could be inserted before the connector H depending uponthe size of the system.

Having briefly described the ap aratus shown in the drawing ,'a detailedescrip tion of the operation will now be given.

For this purpose it will be assumed that thesubscrlber at substation Adesires to call the subscriber at. substation A. In order to do this'thesubscriber at substation A will remove his receiver and" operate hiscalling device S in accordance with the two digits of the number of thedesired called subscriber. When the receiver is removed at substation A,a circuit .is completed for the line rela 16 of the line switch C overthe line con uctors 11 and 12 in series. Re

lay and the said motor magnet. The operation of the line switch C nowdepends upon whether the trunk line with which the switch wipers 27-29,inclusive are in engagement is busy or idle. Assuming that the trunkline is busy, there will be a ground 1 potential present upon the testcontact en-,

gaged by the test wiper 28 and the motor' magnet ing supplied withdirect ground via the said test wiper will operate as a buzzer toadvance the switch wipers step b step in search of an idle trunk line.

owever, it will be assumedthat when the receiver is removed atsubstation A the wipers of the line switch 0 are in engagement with thetrunk line comprisin conductors 30-32, inclusive, and it will assumedfurther that this trunk line is idle. Under these conditions,immediately following the energization of the line relay 16, switchingrelay 15 ener izes. It may be stated at this point that t e switchingrelay 15 is of sufliciently high resistance to pre; vent theenergization of the motor magnet 17 in series wlth it. Upon energizing,relay 15 disconnects the line conductors 11. and 12 of the substation Afrom the winding of the line relay 16 and from ground, respectively, andextends them by way of armatures 20 and 22, wipers 27 and 29, bankcontacts 30 and '32, normally closed springs controlled by armatures 58and 59, to the upper and lower windings of the line relay 51 of theconnector H.

The line relay 51 is immediatel energized over the calling-line loop anu 11 operating, completes the circuit of the s ow loo acting releaserelay 52. Relay 52, upon 0 crating, prepares the impulsing circults oithe connector H at armature 67and at armature 66 places ground onrelease trunk conductor 49 thereby establishin a holding circuit forline switch C. T is circuit extends by way of the test contact 31, testwiper 28, armature 21 and its front contact, winding of the switchingrelay 15, and thence through the winding of the motor magnet 17 tobatter This circuit serves to maintain the switc ing relay 15 operatedthroughout the connection. A branch of the holding circuit also extendsby way of the private normal conductor 35 to multiply connected testcontacts in the banks of connector switches which have access to theline of the substation A whereby the said line is protected fromintrusion in the usual manner.

The subscriber at substation A may now operate his calling device inaccordance with the first digit of the desired called subscribersnumber. By this operation a series of interruptions is produced in thecircuit of the line relay 51 of the connector H and this relay retractsits armature a plurality of times in response thereto. At eachretraction of its armature 60, an impulse of current is sent from groundby way of the armature 60 and itsvback contact, armature 67 and itsfront contact, ofi' normal springs 63 and 62, through the winding of theslow acting relay 53 and thence through the winding of the verticalmagnet 88 to battery. The above is the circuit over which the firstimpulse to the vertical magnet is sent. However, upon the first verticalstep of the switch, the off normal springs are shifted and the remainingimpulses to the vertical magnet traverse a new circuit'which is the sameas the one previously traced except that it includes the off normalsprings 63 and 6-4 and armature 58 and its front contact, relay 53 beingnow in an operated position. Vertical magnet 88 operates to raise theswitch wipers 90-92, inclusive, step by step until they are placedopposite the level of bank contacts in which is located the contact setassociated with the line of the called substation A. The slow actingrelay 53 is ener- .gized in series with the vertical magnet andmaintains its armature attracted throughout the vertical movement of theswitch, and at the termination thereof deenergizes and transfers theimpulsing circuit to the rotary magnet 87.

The calling subscriber may now operate his calling device in accordancewith the next and final'digit of the desired number. As before, a seriesof interruptions is produced in the circuit of the line relay 51, whichdeenergizes a corresponding number of times, each time'sending. animpulse of current over the following circuit: ground by way of armature60 and its back contact, armature 67 and its front contact, ofi normalsprings 63 and 64, armature 68 and its back contact, back contact andarmature 75, armature 84 and its back contact, through the winding ofthe rotary magnet 87 to battery. The rotary magnet 87 operates to rotatethe switch wipers into engagement with the set of bank contactsassociated with the line of the desired substation A, which we willassume, are the bank contacts 93-95, inclusive. The slow actin relay 56is energized in multiple with t e rotaryv magnet and operates at itsarmature 79 to connect the test wiper 91 with the test relay 5'5.

Assuming that the line of the substation A is idle, there will be noground potential present upon the test contact 94 engaged by the testwiper 91 and no circuit will be completed for the test relay 55. Then,followmg the deenergization of the slow acting relay 56, a circuit iscompleted which may be traced from ground on release trunk conductor 49,armature 74 and its back contact, lower winding of the switching relay57, back contact and armature 79, test wiper 91, test contact 94,through the winding of the switching relay 96 of the line switch C, andthence through the winding of the motor magnet 98 to battery. Relays 57and 96 are energized over this circuit. However, due

to a mechanical interlocking device controlled by the armature of theline relay 97 which is now normal, the switching relay only partiallyoperates its armatures, that is, enou h to disconnect the line of thesubstation from its normal batter and ground connections in the lineswitch 6'. Relay 57, upon energizing, establishes a locking circuit foritself at its armature 83 and at its armatures 83 and 85 completes theringing circuit. Ringing current from the generator Gen isintermittently applied to the line of substation A until the subscriberthereat responds.

When the called subscriber removes his receiver, the ring out oif relay54 is energized over the called line loop and, upon operating,establishes a locking circuit for itself at its armature 71, at itsarmatures 70 and 72 opens the ringing circuit, and at the front contactsof these armatures finally completes the talking connection. Talkingbattery is supplied to the called subscriber from the windings of theback bridge relay 50 which is immediately energized over the called lineand operates to reverse the normal current flow over the calling lineloop for supervisal or metering purposes. The. conversation may now takeplace between the calling subscriber at substation A and the calledsubscriber at substation A, the calling subrelease magnet '86 of theconnector H. The

1 H to normal in the usual manner.

magnet 86 operates to restore the connector Upon ground being removedfrom the release trunk conductor 49 the holding circuit of the switchingrelay 15 in the line switch C is opened and thls rela then deene'rgizesthus restoring the line swltch to normal position. 1 a

The above is the normal operation of the system when the line of thecalled-substation A is idle and follows the usual ractice. However,should the line of the su station A be busy either from initiating thecall or from being called, it becomes necessary in accordance with thefeatures of the invention to notify the subscriber at substation A thathe is being called. This operation will now be described. For thispurpose it will be assumed that when the switch wipers 90-92, inclusive,of the connector H are rotated into engagement with the contact setassociated with the line of the substation A, the called line is busy.Under these conditions, there will be a ground potential present uponthe test contact 94. This ground will be laced on the test contact 94whether the su scriber at substation A is busy from being called orinitiating the call. If initiating a call, contact 94 will be groundedby way 'of'the release trunk conductor extending to the connector inuse;

. while if the line of the substation A is being called, there will be aground potential on the contact 94 from the test wi er of the connectorswitch which has estabhshed connection with the line. Immediately u nthe switch wipers 90-92, inclusive, belng rotated into engagement withthe bank contacts 93-95, inclusive, a circuit is completed which extendsfrom the grounded test contact 94 b way of test wiper 91, armature 79and its ont contact, arma ure' 81 and its back contact, and thence tough the winding of the test relay 55 to battery. Relay 55, uponenergizing, prepares a point in its ocking circuit at armature 74 whichis closed immediately upon the "deenergization of the slow acting relay56. Another result of the energization of relay 55 is that a busytonefrom the busy machine is placed on the lower heavy talking conductorat armature 76 which is audible to the calling subscriber. A stillfurther result of the 'energization of relay 55 is that a light tone isplaced on the called subscribers line over a circuit extending from thetone conductor 119, ar-mavture 73 and its front contact, armature 77 andits back contact, back contact and armature 80, wi or 90, bank contact93, and thence over the me of the called substation A. This tone servesto inform the subscriber at substation A that he is being called, but itis quite low and does not appreciably interfere with the conversation.When the subscriber at substation A hears the busy tone,

he will replace his receiver upon the switchhook and then release theoperated switches in the same manner as was described hereinbefore. 'Thesubscriber at substation A being notified that he is being called by theabove mentioned tone will, in all probability, 1

terminate the conversation as soon as possible thereby rendering hisline accessible to be called and thus lessening the time during whichhis line is held busy.

At this point the operation of the interrupter I in producing the lowinduced tone which is placed on the busy called subscribers line will bedescribeda little more in detail. The interrupter I is made up of twocoils 100 and 101 above which is pivoted I an armature, 105. Attached tothe armature'105 is a swinging pendulum 102. As the pendulum 102 movesback and forth it closes the circuit of the coils 100 and 101 at theproper point in its are as it is connected to battery. That is, assumingthat the pendulum 102 is moving to the right under influence of the coil100 it will break contact with the contact 103 thereby opening thecircuit of the coil 100 and shortly after close the contact 104 therebyclosing thecircuit of the coil 101. Upon energizing the coil 101attracts the armature 105 an causes the. pendulum '102 to move in theopposite direction. The s eed of the pendulum may be regulated by meansof the weight 125 which is held in position by the set screw 126. Theweight 125 is preferably quite heavy so as to make the pendulum 102 slowmoving. Each time the pendulum moves back and forth, its upper endengages the spring 109 and causes it to break contact with the spring106. However, there is a short interval when all the three contacts aremaking, that is, the pendulum 102, the spring 109 and the spring 106. Atthis instant, there is an impulse of battery sent over the conductor.123 and through the coil 111 to round. As the pendulum 102 and thespring 109 make and break contact, the condenser 112 is charged anddischarged through the upper winding of the coil 110. The currentfluctuation in the coil 110 serves to induce a secondary alternatingcurrent large capacity as compared with the condenser 113. Also theupper winding of the coil 110 has a great many more turns on its windingthan has the lower winding of the coil 110. This is so as to get asuflicient volume of pulsating current to su ply a number of tone leads.The tone lea 119 is common to a group of connector switches which haveaccess to 100 lines. In the case of a large system where there are anumber of groups of 100 lines each group of connectors will be suppliedwith a tone lead ,such as 120 and 121 and a condenser individual to eachlead such as 114 and 115. It will be seen that the above constructionwill give a slow click tone signal to any subscriber on a called busyline, which is so light that it does not interfere in any way with theconversation.

Having full described and ascertained the features 0 the invention, whatis considered to be new and desired to have protected by Letters Patentwill be pointed out in the appended claims.

What I claim is:

1. In a telephone system, a calling and a called line, an automaticswitch controlled over said calling line to connect with said,

called line in an attempt to establish a talking. connection therewith,a switching relay for connecting the wipers of said switch, a test relayresponsive in case the called line is busy to open the circuit of saidswitching relay, a source of signalling current, and a circuitcontrolled by said relays jointly for connecting said source with thebusy called line.

2. In a telephone system, a calling and a called line, an automaticswitch controlled over said calling line to connect with said calledline in an attempt to establish a talking connection therewith, aswitching relay for connecting the wipers of said switch, a test relayresponsive in case the called line is busy to open the circuit of saidswitchin relay, a source of signallin current, an a circuit forconnecting sai source to one of the wipers of said switch to signal thecalled subscriber while his line is busy, said circuit includingnormally closed contacts on said switching relay and normally opencontacts on said test relay.

3. In a telephone system, a calling and a called line, an automaticswitch controlled over said calling line to connect with said calledline in an attempt to establish a talk ing connection therewith, a testrelay in said switch effective to prevent the completion of such talkingconnection if the called line-is busy, a source of busy signallingcurrent, another source of signalling current, circuits for connectingthe first of said sources to the calling line and the second of saidsources to the called line, and contacts on said test relay included inboth said circuits for closing the same when the test relay isenergized.

In witness whereof, I hereunto subscribe my name this 9th day of June,A. D. 1921.

' WILLIAM A. BENSON.

